Traditional fuel injectors have a molded plastic surround associated with the electrical terminals of the power group to form an electrical connector. Some fuel injectors also have some overmold extend axially down the outer surface of the power group, for aesthetics and/or for ease of part identification and/or for encapsulating internal components. Historically, most injector designs have coated exposed metal surfaces of the power group and valve group with a plating or paint to meet the requirements that the injector be able to withstand numerous hours of a corrosive salt spray environment and still display no visible signs of rust.
Plating and painting require careful process control to insure that an even thickness of plating/painting occurs only in the areas desired: surface preparation and cleanliness can be a concern, and uneven covering of the surface results in failure to protect from corrosion. If the plating is applied prior to assembly of subcomponents, contamination of the interior of the injector can result in failed durability or leaking units. Plating or painting after subassembly means subjecting the final calibrated and flowed injector to mishandling or contamination issues which could also result in failed units. Additionally, one area of an injector where it is typically difficult to insure corrosion protection is the mating area between the power group and the valve group.
Some recent fuel injectors have utilized overmold over the entire outer surface of the power group for corrosion protection. Although this is a beneficial solution for elimination of the plating and painting concerns, it has two main drawbacks. The overmolding requires that the outer diameter of the injector be increased. This is contrary to recent trends in engine compartment down-sizing which have dictated that any noticeable increase in the outer diameter of a component will not be acceptable. The holding location for the overmold process typically requires that the inner surface of the injector be contacted. This creates the potential for creation or retention of contamination which will be internal to the injector after the assembly process, possibly resulting in leaks, erratic flow or a durability flow shift.
The present invention is related to a power group construction and method that avoids contacting the inner surface of the power group during the process of creating the overmold. In the disclosed embodiment, this occurs by providing a stepped outer diameter at the lower end of the outside surface of the power group.
Various features, advantages and the inventive aspects will be seen in the ensuing description and claims which are accompanied by drawings that disclose a presently preferred exemplary embodiment of the invention according to the best mode contemplated at the present time for carrying out the invention.